Combined elevator and tail gate for trucks



Dec. 14, 1954 K. Y. MESSICK 2,696,923

COMBINED ELEVATOR AND TAIL GATE FOR TRUCKS Filed Feb. 1, 1950 3Sheets-Sheet 1.

INVENTOR Hawaii! Y MES-SICK ATTORNEYS Dec. 14, 1954 K, Y. MESSICK2,696,923

COMBINED ELEVATOR AND TAIL GATE FOR TRUCKS Filed Feb. 1, 1950 5Sheets-Sheet 2 INVENTOR HAWAN Y lflsssicz ATTORNEYS I Dec. 14, 1954 K Y,MESSICK 2,696,923

COMBINED ELEVATOR AND TAIL GATE FOR TRUCKS Filed Feb. 1, 1950 I 4 5Shets-Sheet :5

all hm?! I (387 Il/I/lII/ll/Il/Kl/ll/l/l/fi/ ll/[II/Il/l/l/l/Ill/ll/Il/ll/ INVENTOR. K12 WHN lfissslcx and tail-gate formingmechanism for trucks.

United States Patent O COlVIBlNED ELEVATOR AND TAIL GATE FOR TRUCKSKirwau Y. Messick, Arlington County, Va., assignor of one-fourth toFrank G. Campbell, Arlington County, Va.

Application February 1, 1950, Serial No. 141,755

11 Claims. (Cl. 214-77) This invention relates to a combinedload-elevating A principal object of the invention is to eliminate theexcessive weight which has been a characteristic of many of the devicesproposed to serve the purpose of my invention.

A further object of the invention is to provide a loadlifting andtail-gate forming platform and improved mechanism for actuating thesame, all of which is built into a simple and complete unit, assembledat the factory, and comprising means for mounting it upon a truckwithout the necessity of drilling holes in the under structure of thetruck as has heretofore frequently been required.

The construction, manner of operation and advantages of-the inventionwill be best understood by reference to the accompanying drawings,wherein:

Figure 1 is a side elevation of the device of the invention showing theparts in lowered position and with the platform, or gate, in section,

Figure 2 is a like view showing the parts in the position that theyoccupy when the platform has been lifted to truck floor level, but withthe platform still in its loadsupporting position,

Figure 3 is a fragmentaryview showing some of the elements of Figure 2,and showing the platform moved to vertical, or tail-gate formingposition,

Figure 4 is a rear elevation of the hangers and their connecting tierods which are secured to the frame members of the truck, and whichserve to pivotally connect the swinging arms and links hereinafterdescribed, to the elevating platform.

Figure 5 is a plan view of the elements of the invention,

Figure 6 is a diagrammatic view, illustrating the motor, pump, hydrauliccylinders, fluid supply lines, and the control valves therefor,hereinafter described,

Figure 7 is an enlarged sectional view through one of thetelescopic'links which holds the platform horizontal during the timethat it is being moved from the position of Figure l to the position ofFigure 2.

Like numerals designate corresponding parts in all of the figures of thedrawings. The particular embodiment of the invention which I have chosenfor purposes of illustration comprises a pair of hangers, each hangercomprising a pair of plates 5 and 6, said plates being welded orotherwise secured upon the end portions of a transverse torque tube 7.This tube not only serves the function of tying the hanger-constitutingplates to each other, but it is so welded to the outer plates 6 thatsaid plates close the ends of the tube, and thus said tube is adapted toserve as a reservoir for the oil, or other fluid,

which is used in the hydraulic system by which the platform is elevated.The tube 7 and the plates 5 have welded thereto a pair of saddles 8, andthese saddles have openings formed therethrough at 9, for the passage oftie rods 11). The upper ends of these tie rods pass through plates 11which rest upon the top of channels 12, these channels representing apart of the chassis of the truck to which the device is to be applied.One of theplates 5 also serves as a mounting for arotary or piston type.

pump 13 and a direct connected motor 14 by which the pump is driven. Theintake of the pump is indicated at 15, leading from tube 7 to the pumpand the dis charge line of thepump is indicated at 16 and leads to 3 twocylinders.

2,696,923 Patented Dec. 14, 1954 pivot pins 17, 18 and 19. The pivotpins 17 and 19 extend only from plate to plate, but the pivot pins 18are extended outwardly beyond the plate 6, as indicated at 18a. Theload-lifting platform 20 may be formed in many different ways. As shownin Figure 1, it comprises a solid metal top plate 21, an outer-edgeangle strip 22, and the torque tube 23 which stiffens it and whichextends throughout its length. A plurality of braces 24 of U shapeextend from the torque tube to the angle strip 22. Heel plates 26 weldedto top plate 21, and to the torque tube 23 carry the pivot pins 27 and28, pins 28 lying below the pins 27. Stout box-like arms 29 arepivotally connected at their outer ends to the pins 27, and arepivotally connected at their inner ends to the pins 17 of the hangerplates. The arms 29 are closed box-like members in cross section, andthey are relatively wide at their rear ends and taper toward their outerends. By making these arms closed, as stated, they are adapted to housethe hydraulic cylinders and their piston rods, indicated at 30 and 31.The piston rods 31 slide in and out of the cylinders in the operation ofthe device, and they are highly polished to secure the necessary closefit to adapt them to retain the high pressures employed in hydrauliclifts. By thus housing these members in the. arms 29, they are protectedfrom.mechan1cal damage,

20 in its horizontal position throughout the time that it' is beinglifted from the ground level position to the floor level position of thetruck. During this elevating movement of the platform, the rods 34 arebottomed in the sleeves 33. That is to say, the links have then assumedthe position in which they are as short as they ever get. This is theposition shown in Figure 7. When in this position, lines through pivots27, 28, 18, 17, and back to 27 constitute parallelograms. However, stoutsprings 35 surround the rods 34, and when load is on platform 20, saidsprings are strongly compressed between the lower ends of the sleeves 33and collars 36, by which the links are pivoted on pins 18a. As long asthere is a load upon platform '20, the relative position of the partswill be that indicated in Figure 2, but when the load has been movedfrom platform 20 over into the body of the truck, the platform may bemanually swung upon pivots 27 to the position illustrated in Figure 3,where, as before stated, it constitutes a tail-gate closure for thetruck. This upward movement of platform 20 is rendered possible by thefact that the link constituted by sleeve 33 and rod 34 is an extensibleone, and further the springs 35 act to thrust the platform 20 to thevertical position of Figure 3, as described. The springs also act tocushion the movement of the tail-gate back to theposition of Figure 2.It requires but a very slight eflfort upon the part of the truck driverto close the tail-gate when it is assisted in its closing movement bythe powerfully compressed springs 35. However, the strength of thespring is such that the weight of the tail-gate will keep it fromtipping upwardly above the horizontal, until manually assisted. The gatemay be provided with a conventional latch to hold it in the position ofFigure 3, if desired,

but the springs render such a latch unnecessary.

Referring now to the diagrammatic Figure 6, it will 'be seen that thefluid pressure line 16 leads to one or more of the hydraulic cylinders30. This is to indicate that a hydraulic cylinder may be used upon onlyone side of the structure where light work is to be done. However, abetter balanced structure is had by using The motor 14 may be drivenfrom the conventional truck battery b, or a separate battery may beprovided. A circuit including wires 37 and 38, push button switch 39,and relay '40, provides means, when the switch 39 is closed, to set themotor and pump in v operation. This pumps oil from the oil reservoir 7into the discharge lines 16. This in turn causes the pistons to move outof their cylinders and to act upon the pins 32 to lift the platform tothe position of Figure 2. Removing the finger from push button 39 causesthe motor to instantly stop. A check valve 41 holds the pressure in theline and holds the gate in its elevated position as long as may bedesired. When it is desired to return the platform to the position ofFigure l for the reception of an additional load, a push button switch4-2 is pressed. This completes the circuit from the positive side of thebattery through switch 32, 42, wire 43, a normally closed solenoid valve44, and to the negative side of the battery at 45. This opens thesolenoid valve and permits the oil to drain out of the lines 16 backinto the oil reservoir 7, whereupon the weight of the platform causes itto descend.

It will be observed that the whole assembly including the hangers, thepump, motor, fluid supply lines, platform and the actuating arms and thelinks, are all ca. ried by the torque tube 7, and thus may be assembledat the factory and placed in position upon a truck by the mereapplication of the tie rods or bolts 10. This, as before stated, avoidsthe necessity of a great deal of laborious work made necessary where thetruck frame has to be drilled to receive special fittings.

The structure herein disclosed is an extremely strong and rigid one, andyet, considering the results achieved, it is very light in comparisonwith the structures here tofore proposed. This mechanism will lift moreload, pound for pound, in comparison with its own weight than any withwhich I am familiar, and that by a very large margin.

The provision of the arms 29 of closed box-like formation, and makingthese arms enough deeper adjacent their heel portions so that they maybe tied together by the transverse torque tube 29a, renders this part ofthe device very rigid and capable of resisting the torsional strainswhich are brought upon the structure when a heavy load is placed nearerone end of the platform 20 than the other. Also, the use of the torquetube 23 in the gate itself renders that structure very rigid and strongin proportion to its weight. It will be understood that the torque tube290 is welded at its opposite ends to the inner side walls of the arms29.

An important feature of the invention resides in the manner in which Ihave related the outwardly thrusting pistons 31 to closed top, box-likearms 29. The points of thrust between 19 and 32 is such that the pistonsthrust upwardly. This is much better than having the piston pull itsarms upwardly because the construction that I have devised leaves thearms 29 wholly closed, thus protecting the cylinders and pistons fromthe weather, and making the use of cam slots in the arms unnecessary.This permits the complete housing of the cylinder by the box-like armsand protects the piston rods from mechanical damage as well as fromdamage by the elements. Attention is directed to the fact that thetorque tube 2%, not only unites the arms 29, but it does this at a pointspaced away from the pivots 17 and toward the outer ends of arms 29.This makes for great rigidity with light weight. The use of a tubeinstead of a bar of equal diameter makes for li ht weight, and yet thepoints of attachment of the tube to the arms is over a diameter equal tothat which would be presented by a solid rod, or bar, of equal diameter.This spacing of the points of attachment of tube to arms, and thespacing of the tube away from the pivot points of the arms, gives astructure of great strength and rigidity. While I have shown the torquetubes as being circular in cross section, they may be other thancircular, if desired. In the platform, the torque tube stitfens andstrengthens the gate to resist the torsional strains when the gate isunevenly loaded. The torque tube 7 mounts the hangers, motor, pump, andall other parts of my attachment, on so rigid a foundation that twistingstrains in the truck body will have no effect whatever upon this unit.Also, it mounts all parts of the invention directly at the rear of thetruck where they are readily accessible. No parts extend forwardly underthe truck to inaccessible places.

It is to be understood that the invention is not limited to theparticular construction shown, but that it includes within its purviewwhatever changes fairly come Within either the terms or the spirit ofthe appended claims.

Having described my invention, what I claim is:

1. In a combined elevating platform and tail gate for vehicles, a pairof hollow box-like arms wider at their inner than at their outer ends, aload carrying platform having vertically spaced pivots at its inner endportion, means pivoting the inner ends of the box-like arms to a truckbody, means pivoting the outer ends of said arms upon the upper pivotsof the platform and a large diameter torque tube extending between andrigidly uniting the inner side walls of the said arms at a pointrearwardly of the fore and aft center of said arms but at a point spacedfrom the rear ends of said arms.

2. A structure of the character described, comprising a load liftingplatform, a pair of arms pivoted at their outer ends to said platformand at their inner ends to a truck body, a pair of telescopic linkspivotally connected at their outer ends to the platform, and at theirinner ends to the truck body, said links, when in their shortestposition, constituting with said arms, parallelograms by which theplatform is held substantially hor izontal while being lifted fromground level to truck fioor level, springs associated with said linkswhich are compressed during the lifting of the platform, and which tendto tip the platform upwardly to tail-gate forming position when the loadis removed from the platform at truck floor level, said extensible linkscomprising rods, and sleeves in which said rods slide, the springssurrounding the rods and engaging the inner ends of the sleeves, saidrods being bottomed in said sleeves when the links are in their shortestand parallelogram forming position.

3. In a device of the character described, the combination of a loadlifting platform, a pair of arms, the outer ends of which are pivotallyconnected with the platform and the inner ends of which are pivotallyconnected to a truck body, said arms being of closed boxlike formation,hydraulic cylinders and pistons housed within said box-like arms andacting to thrust the outer portion of said arms upwardly when pressurefluid is admitted to the cylinders, and a torque tube extending betweensaid arms and rigidly aflixed to the inner side walls of said box-likearms, at a point materially in advance of the rear ends of said arms.

4. In a device of the character described, the combination of a loadlifting platform, a pair of arms, the outer ends of which are pivotallyconnected with the platform and the inner ends of which are pivotallyconnected to a truck body, said arms being of closed boxlike formation,hydraulic cylinders and pistons housed within said box-like arms andpivotally connected to the truck body and said arms at points to causethem to act to thrust the outer portion of said arms upwardly Whenpressure fluid is admitted to the cylinders, a pair of telescopic links,the outer ends of which are pivotally connected to said platform and theinner ends of which are pivotally connected to the truck, means carriedby the said links comprising springs tending to extend them and tendingto tip the platform upwardly upon its pivotal connection with the saidarms, said links comprising rods, and sleeves which slide upon saidrods; said links, when in their shortest position being ofsuch length asto constitute with said arms parallelograms which maintain the platformhorizontal during its lifting movement.

5. A structure of the character described, comprising a load liftingplatform, a pair of arms pivotally connected at their outer ends to theheel of said platform, and a hydraulic cylinder and piston housed in oneof said arms and pivotally connected to the arm and to a truck carriedpart and acting to thrust the arm upwardly from a point below said arm,said arms being of hollow, box-like formation and being materially widerat their inner than at their outer portions, and a rigid torque tubeuniting the inner sides of said arms at points materially spaced fromthe inner ends thereof.

6. A unit for mounting a hydraulically actuated lift gate on a truck,comprising a transversely arranged torque tube with hangers at the outerends thereof, said tube being closed to constitute a reservoir, pivotscarried by said hangers, an electric motor and pump driven by said motormounted to be moved bodily with said tube and to be positioned by thesecuring of the tube to a truck body, andmeans for securing the tube toa truck body.

7. A lift gate for trucks, comprising a torque tube, a plurality ofrearwardly extending braces secured to the torque tube, a plurality fforwardly extending heel plates secured to the torqu: tube and carryingpivots and a top plat eextending across the heel plates, torque tube andsaid braces, and a member extending throughout the length of the gate towhich the rear ends of the braces and the rear portion of the top plateare secured.

8. In a hydraulic power lift for trucks, a pair of supporting bracketsattached to the truck body, one at each side of said body and at therear end thereof, each of said brackets carrying three pivots, spacedthroughout the height of the brackets, a load lifting platform providedat each side with a pair of pivots at its heel portion one above theother, a pair of arms pivoted at their outer ends to the uppermost ofsaid pivots and pivoted at their inner ends to the uppermost truckcarried pivots, a pair of links pivoted at their inner ends to theintermediate ones of the truck carried pivots and pivoted at their outerends to the lowermost pivots at the heel of said platform and formingwith said arms parallelograms, a pair of hydraulic cylinders andpistons, said pistons being pivoted on the lowermost truck carriedpivots and the pistons being pivoted to said arms at a point nearer theouter ends of said arms than to the inner end thereof, the dispositionof the pivots being such that when pressure fluid is admitted to thecylinders the thrust is from beneath said arms, upwardly.

9. A structure as recited in claim 8 wherein the links comprisetelescopic rods and sleeves and springs associated therewithcompressible under the load lifting action, the parts of said linksbeing of such dimensions that when the springs are fully compressed theeffective length of the links is such as to cause them to constitutewith said arms parallelograms, said springs tending to further extendthe links to tip the platform upwardly at'the conclusion of the liftingoperation.

10. A structure of the character described, comprising a load liftingplatform having an upper and a lower pivot point at its inner endportion, a pair of upper and lower truck carried pivots, a load liftingarm pivoted at its inner end to the upper truck carried pivot and at itsouter end to the upper platform carried pivot, hydraulic means acting toswing the arm and platform upwardly from the pivoted inner end of saidarm, an extensible link pivoted at its inner end to the lower truckcarried pivot and at its outer end to the lower platform carried pivot,said points being so located and the length of the link and arm beingsuch, that when the link is in its shortest position, it constituteswith said arm the sides of a parallelogram, and a spring carried by saidextensible link and so disposed as to be placed in energy storingposition as the parts of the link move to the shortest position of saidlink, said spring tending to extend said link and to thereby tip theplatform upwardly upon its upper pivot point.

11. A structure of the character described comprising a load liftingplatform, a pair of lifting arms pivoted at their outer ends to saidplatform and at their inner ends to truck carried pivots, linkspivotally connected at their outer ends to the platform at a point belowthe pivoted connection between said platform and the lifting arms, andat their inner ends to truck carried pivots, said links when telescopedto their shortest positions constituting with said arms, parallelogramsby which the platform is held substantially horizontal while beinglifted from ground level to truck floor level, and a compression springcarried bodily by at least one of the extensible links and so related tothe link as to be compressed by the telescoping of the link, said springtending to extend the length of the link and tip the platform upwardlyupon its pivotal connections with said arms and to tail gate formingposition, when the load is removed from the platform at tail gateforming position.

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